To efficiently transfer or record a video, an image coding apparatus configured to generate coded data by coding the video and an image decoding apparatus configured to generate a decoded image by decoding the coded data are used.
Examples of specific video coding scheme include schemes proposed in H. 264/AVC and High-Efficiency Video Coding (HEVC).
In such a video coding scheme, an image (picture) included in the video is managed by a layered structure including a slice obtained by splitting the image, a coding unit (which may be abbreviated as “CU (Coding Unit)”) obtained by splitting the slice, a prediction unit (PU) that is a block obtained by splitting the coding unit, and a transform unit (TU), and is coded/decoded for each CU.
Furthermore, in such a video coding scheme, generally, a prediction image is generated based on a locally decoded image obtained by coding/decoding an input image, and a prediction residual (which may be referred to as “difference image” or “residual image”) obtained by subtracting the prediction image from the input image (original image) is coded. A method of generating the prediction image includes an inter-screen prediction (inter prediction) and an intra-screen prediction (intra prediction).
Furthermore, an example of a recent video coding and decoding technology includes Non Patent Literature 1.
Furthermore, in recent years, as a method of splitting a Coding Tree Unit (CTU) included in the slice, in addition to QT split where the CTU is split in a quad tree fashion to obtain a CU, BT split where the CTU is split in a binary tree fashion to obtain a CU is introduced. The BT split includes a method of horizontally splitting the CTU and a method of vertically splitting the CTU.